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The identification of powdery mildews on Brassica chinensis var. oleifera in China

Shuyan Liu: Jilin Agricultural Univ

<div><em>Brassica chinensis </em>var. <em>oleifera </em>(Brassicaceae) is a widely consumed vegetable in China. Severe powdery mildews on them were observed in Jilin Agricultural University, China in May 2017. White mycelia densely covered both the upper and the lower side of leaves, stems and pods. The teleomorph stages of the fungus were not found. The morphological characteristics of the fungus were consistent with <em>Erysiphe cruciferarum</em>. To confirm the identification, the complete ITS region including 5.8S rDNA and partial 28S rDNA sequences were amplified and sequenced. The resulting 607 bp ITS sequence (MF192845) and 629 bp partial 28S rDNA sequence (MF192846) showed 100% identity with <em>E. cruciferarum</em> from <em>Brassica juncea</em> (KM260718) and <em>Cardaria draba</em> (AB102944), respectively. The pathogenicity tests were conducted by gently pressing a diseased leaf onto three asymptomatic leaves. Three uninoculated leaves served as controls. The plants were maintained in the lab at room temperature (23 to 25 °C) and relative air humidity of 60 to 70%. Symptoms developed 5 days after inoculation. No symptoms developed on the control plants. Powdery mildew on <em>B. chinensis </em>var. <em>oleifera</em> has been reported as <em>E. cruciferarum </em>only in Estonia, Germany, Switzerland on Sysmatic Mycology and Microbiology Laboratory Fungus-Host Database. To our knowledge, this is the first record of <em>E. cruciferarum</em> on <em>B. chinensis </em>var. <em>oleifera</em> in China and the results extended the distribution and the host range of <em>E.</em><em> cruciferarum</em>.</div>